1. Field of the Invention
The present invention relates primarily to a data transfer apparatus, a data transfer method, and an information processing system and, more particularly, to a data transfer apparatus such as a server machine in a client-server system, a data transfer method and a program for data transfer or the like from a server machine to a client machine, and an information processing system such as a client-server system.
2. Related Background Art
In recent years, increasing efforts have been put into the development of client-server systems as the information processing systems for use on internets or other types of networks. A client-server system is configured so that a server machine (hereinafter referred to as a xe2x80x9cserverxe2x80x9d) retains and manages major data in a unified manner and a client machine (hereinafter referred to as a xe2x80x9cclientxe2x80x9d) can access such data at any time. For example, when a server and a client are connected on an internet for the purpose of accessing information by a world wide web (WWW), which serves as a wide area information system, a server creates document data in a hypertext described in a hyper text markup language (HTML), while the client receives the document data by means of a communication protocol called xe2x80x9chyper text transfer protocolxe2x80x9d (HTTP). Thus the document data is displayed on a display unit of the client.
Most document data transferred from the server to the client are usually composed of a plurality of objects including embedded objects and linked objects. More specifically, as shown in FIG. 8, for example, a page A is composed of an embedded object b and c, and the data on a page D to which the page A is linked, i.e., a link object d, in addition to a main text a indicative of main contents. Furthermore, the page D to which the link object d is linked frequently has an embedded object f in addition to a main text e.
In general, the embedded objects b and c, or the link object d are retained in a separate file from that on the page A. Hence, in many cases, the portion corresponding to the embedded objects b and c, or the link object d in the page A includes only the information for referring to the embedded objects b and c, or the link object d. For this reason, the data on the page A is sequentially transferred time-wise from the server to the client according to the procedure illustrated in FIG. 9.
More specifically, when the client issues a connection request to the server and the connection between the client and the server is implemented, the client first reads in all data contained in the page A, then analyzes the contents of the data to check for the presence of the embedded objects b and c, or the link object d. The client then issues three connection requests to the server at the same time in order to read in the embedded objects b and c, and the data on the page D to which the link object d is to be linked that are retained in a separate file.
On the other hand, data transfer from the server to the client on the network is performed on a basis of packet of a predetermined length of data. Therefore, to implement data transfer to a plurality of connections (three connections in this case), the network is evenly used for the respective connections, the embedded objects b and c, and the data on the page D are read in time-sharing mode.
To be more specific, when each datum consists of three packets, as shown in FIG. 9, an embedded object b1, an embedded object c1, and data D1 on the page D are first read in sequence into the client. Then, an embedded object b2, an embedded object c2, and data D2 on the page D are read in, and further, an embedded object b3, an embedded object c3, and data D3 on the page D are read in. When all the data on the page D that is divided into three sections has been read in, the client issues a connection request to the server in order to read in an embedded object f that is embedded in the page D and retained in a separate file from that of the page D.
Page A and the embedded object f are also transferred from the client to the server by being divided in a plurality of sections based on packets. There is no other network connected to the server at the same time, so that the network is monopolistically used for transferring the data.
In the data transfer method described above, however, the embedded objects b and c, and the data on the page D to which the link object d is to be linked are read in sequence according to the reading order in units of packets, so that no particular portion of data can be preferentially taken out. For example, the embedded objects b and c may be image data providing cut-in illustration for decorating the main text a of the page A. In such a case, a request for giving a higher priority to referring to the main text e of the page D than the embedded objects b and c may be made. Since the conventional data transfer method is adapted to read data on a basis of packet in the time-sharing mode as discussed above, it has been impossible to refer preferentially to the data of the main text e of greater significance.
The use of networks based on radio transmission has been becoming widespread these days; however, disconnection of lines during data transfer based on the radio transmission may happen due to radio waves failing to reach in the middle of transfer. In this case, if, for example, the line between a client and a server is disconnected at time T1 of FIG. 9, then the client must send a request for reconnection to the page D to the server so as to read the data of the page D, or restart from reading the data of the page A, depending on a situation, thus posing a problem of inconvenience.
Accordingly, it is an object of the present invention to provide a data transfer apparatus, a data transfer method, and an information processing system that are capable of preferentially acquiring data of greater significance.
It is another object of the present invention to provide a data transfer apparatus, a data transfer method, and an information processing system that are capable of obviating the need of reconnection for rereading as much as possible even if a line is disconnected in the middle of communication.
According to one aspect, the present invention which achieves these objectives relates to a data transfer apparatus including: priority setting means for assigning a priority to each of a plurality of transferable data; and transfer means for transferring a plurality of data for which a transfer request has been issued to a terminal according to an order based on the priorities assigned to the respective data by the priority setting means.
According to another aspect, the present invention which achieves these objects relates to a data transfer method including the steps of: assigning a priority to each of a plurality of transferable data; and transferring a plurality of data for which a transfer request has been issued to a terminal according to an order based on the priorities assigned to the respective data.
According to still another aspect, the present invention which achieves these objectives relates to a computer-readable storage medium storing a data transfer program for controlling a data transfer apparatus to perform data transfer to a terminal via a network, the program including codes for causing the computer to perform the steps of assigning a priority to each piece of a plurality of transferable data, and transferring a plurality of data for which a transfer request has been issued to a terminal according to an order based on the priorities assigned to respective data.
According to yet another aspect, the present invention which achieves these objectives relates to an information processing system having a data transfer apparatus and a terminal connected via a network, wherein: the data transfer apparatus includes priority setting means for assigning a priority to each of a plurality of transferable data, transfer means for transferring a plurality of data for which the terminal has issued a transfer request to the terminal according to an order based on the priorities assigned to the respective data by the priority setting means; and the terminal includes requesting means for issuing a request for transfer of a plurality of data to the data transfer apparatus, and receiving means for receiving data transferred from the data transfer apparatus.
Other objectives and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.